1. Field of the Invention
The present invention relates to a transmission device for configuring a communication network in a ring type or cascade type topology, wherein the respective transmission devices are connected to a specified network.
2. Description of the Related Art
Over the recent years, a network (which will hereinafter be referred to as an RPR network) utilizing a transmission technology called RPR (Resilient Packet Ring) has come to be employed.
As schematically illustrated in FIG. 11, this RPR network is a network having an architecture in which a plurality (six pieces of devices in FIG. 11) of transmission devices 50 (50A trough 50F) are connected in a ring configuration (ring topology) via 2-system transmission paths.
Then, the RPR network is a network (the network enabling bands to be utilized more effectively than by SONET/SDH (Synchronous Optical Network/Synchronous Digital Hierarchy) in which one-side transmission path is dedicatedly used for recovery from a fault) enabling simultaneous data flows to the 2-system transmission paths, and hence a variety of transmission devices 50 capable of building up the RPR network are developed.
In the RPR network using the existing transmission devices 50, however, each of the transmission devices 50 judges whether a certain multicast packet (which will hereinafter be abbreviated to an MC packet) transmitted (forwarded) by a host to all the transmission devices 50 should be dropped (flowed onto a LAN) or not.
Therefore, in the RPR network using the existing transmission devices 50, as schematically shown in FIG. 12, when forwarding the MC packet, some of the transmission devices 50 execute a process of forwarding to the next transmission devices 50 the MC packet that is not dropped by any of the subsequent transmission devices 50 (which is, namely, the MC packet essentially having no necessity of being forwarded).